In E. coli, the gene for tRNA Trp is located in an rRNA operon. These genes have been isolated on a specialized transducing phage which provides a very favorable system for analysis of these genes and their products. A genetic and biochemical analysis of tRNA Trp will follow preparation of tRNA Trp molecules which contain sequence alterations at sites which affect the function of tRNA Trp during protein synthesis. Structural alterations will be correlated with defects in function of the tRNA in the steps involved in protein synthesis. These altered tRNAs can also be analyzed for function in vivo. They will be used to isolate mutations in genes which specify RNases, and in genes involved in regulation of tRNa and rRNA synthesis. In addition, the question of polarity in rRNA will be addressed using a biochemical approach, with the possibility of using the genetic system afforded by tRNA Trp, to define and analyze unique aspects of rRNA transcription.